Sugar recovery method and apparatus

ABSTRACT

A METHOD AND APPARATUS FOR PURIFYING A SUGAR BEARING SOLUTION SUCH AS MOLASSES TREATES THE IMPURE SOLUTION WITH BAUXITE PRIOR TO THE PASSAGE THREOF TO AN ION EXCLUSION RESIN.   D R A W I N G

JUL 16 1973 F. zlEvERs SUGAR RECOVERY METHOD AND APPARATUS 2 Sheets-Sheet l Filed Feb. 22. 1971 Jn 16, 1973 J. F. zIEvERs 3,711,329

SUGAR RECOVERY METHOD AND APPARATUS Filed Feb. 22. 1971 2 Sheets-Sham 2 ION EXCLUSION wf@ HEEL/ 5- United States Patent O ABSTRACT F THE DISCLOSURE A method and apparatus for purifying a sugar bearing solution such as molasses treats the impure solution with bauxite prior to the passage thereof to an ion exclusion resin.

The present invention generally relates to a method and apparatus for removing ionic and large molecular impurities from an impure sugar bearing solution, and it relates more particularly to a new and improved method and apparatus which may be used to extract a substantially pure liquid sugar solution from molasses.

The use of an ion exclusion resin to separate sugar molecules from ionic and other impurities in a sugar bearing solution is known and has met with some success. For example, Pat. 3,214,293 to Mountfort discloses such a system particularly adapted to the treatment of affination syrup. Similarly, P'at. 2,937,959 discloses an ion exclusion system for use in recovering sugar from molasses. Pat. 2,890,972 to Wheaton discloses another such system. In all of these systems it is necessary to first treat the impure sugar solution with an ion exchange resin before the ion exclusion step to prevent premature fouling of the ion exclusion resin.

An object of the present invention is to provide a new and improved method and apparatus for eliminating the use of an ion exchange resin and associated regeneration equipment ahead of the ion exclusion step.

Another object of the present invention is to provide a less expensive method and apparatus for recovery sugar from impure sugar solutions.

A further object of the present invention is to provide a new and improved apparatus utilizing bauxite in an ion-exclusion sugar recovery process.

Briefly, the above and further objects may be realized in accordance with the present invention by treating the impure sugar bearing solution with activated bauxite prior to the passage thereof to an ion exclusion resin. In one embodiment of this invention, granular activated bauxite is mixed with the impure solution and then filtered out before the ion exclusion step. In another embodiment the impure solution is passed through a bed of activated bauxite prior to the ion exclusion step.

Further objects and advantages and a better understanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic ow diagram of a system using the process of the present invention to purify a sugar solution such as molasses; and

FIG. 2 is a schematic flow diagram of another system embodying the present invention.

Referring now to the drawings and particularly to FIG. 1 thereof, an impure sugar solution such as molasses is supplied from a line to a mixing and heating tank 11. A purified, dilute aqueous solution of sugar is supplied to the tank 11 through a line 12 and particulate activated bauxite at mesh size of about 100 is supplied to the tank 11 by a line 13. A motor driven mixer 14 is disposed in the tank to thoroughly mix the bauxite particles with the solution and a heating coil 15 immersed in the solution is fed with steam to heat the solution in the tank to a ice temperature within the range of about 170 to ISO-degrees F. The impure sugar solution will generally have a relatively high Brix value as, for example, a value of about in the case of molasses. It is desired that the effluent from the tank have a Bn'x value of about 60, and therefore, additional water may be added to the tank 11 if the sweet water supplied through the line 12 is insuicient to reduce the Brix value to that desired.

The effluent from the tank 11 is pumped by a means of a pump 17 through a line 18 to a filter 19 wherein the solids entrained in the impure sugar solution are removed. The filter 19 is a mechanical type filter and may be of the type described in United States application (Henry Schmidt, In), Ser. No. 65,393, led Aug. 20, 1970. The efliuent from the filter 19 flows through a line 20 into a column 21 containing a bed of an ion exclusion resin. This resin may be of either the anion or cation type. At the present time, however, because of the relative costs of cation and anion exchange resins, it is preferable to use a cation resin for ion exclusion purposes. Any suitable resin, such as, for example, a strongly acid cation exchange resin comprising a sulfonated styrene-divinylbenzene polymerizate having a cross-linkage or percent of divinylbenzene in the hydrogen form no greater than four and a mesh range of 50 to 100, i.e., a particle size of .149 to .297 millimeter. One such resin is sold by Dow Chemical Company under the trade name Dowex 50X4. The ion exclusion process is carried out in the tank 21 in the usual manner as described, for example, in Pat. 3,214,293, Mountfort. In this process the tank 21 is substantially filled with the resin particles and the sugar molecules are separated from the larger particles such, for example, as the color bodies by virtue of the sugar molecules being absorbed into the gel Within the resin beads while the other solutes occupy the interstitial space between the resin particles. After a sufficient time has elapsed to permit the resin beads to become saturated with the sugar molecules, water from a line 22 is owed through the tank. Initially, the efiiuent from the tank 21 is an aqueous solution highly concentrated with the impurities contained in the interstitial liquid. As the ow of water through the tank 21 continues, the concentration of the impurities diminishes as the water begins to displace the sugar molecules in the resin beads. At this time the eluent is a sugar bearing solution having a considerably greater purity than the impure sugar solution initially supplied to the system and is usually retained for further purification.

As the flow of water continues and all of the impurities have been washed from the tank 21, the efliuent becomes a highly purified sugar solution. This fraction is fed through a line 23 to a second mixing tank 24 Where it is mixed with bauxite fed to the tank 24 through a line 25 and with activated carbon fed through a line 2'6. A suitable motor operated mixer 27 is disposed in the tank to thoroughly mix the bauxite and carbon with the purified sugar solution. As the flow of water through the tank 21 continues, the concentration of sugar effluent decreases and when it falls below about 40 degrees Brix the effluent is connected by suitable valve means (not shown) to the line 12 so that it is returned to the original mixing tank 11 at the head of the system wherein it is mixed with the initial impure sugar solution. The eiuent from the tank 24 is pumped by a pump 29 through a line 30 to a filter 31 wherein the activated carbon particles and the bauxite particles are removed. The effluent from the filter 31 flows through a line 32 to an evaporator 33 wherein water is evaporated from the sugar solution so that the effluent from the evaporator 33 which ows through line 34 to a storage tank 35 has a Brix value of between sixty and seventy. The solids, i.e., bauxite and carbon particles ltered from the sugar solution by the filter 31 are fed to the line 13 from which they flow into the mixing tank `10 at the head of the system. The solids which are removed by the lilter 19 are fed through a line 37 to a pair of settling tanks 38 and 39. The tanks 3'8 and 39 are alternately filled and retain the solids for a suflicient time to permit the liquid carried thereby to, settleto the bottom of the tank from which it is fed through a line 40 to a suitable retention tank 41. The solids from the tanks 38 and 39 vare dropped onto a conveyor belt 42 suitably driven by a motor 43 and fed to a kiln 45 wherein the bauxite particles are purified by burning otf the impurities which were captured thereby in the mixing tank 11. Also, the carbon particles are disintegrated in the kiln 45.

The thus purified particulate bauxite from the kiln 45 is fed by gravity to a hopper 46 from which it is pumped by a pump 47 through the line 25 to the second mixing tank 24.

Referring now to FIG. 2, the impure sugar solution is supplied from the line `50 to a heating and mixing tank 51 to which a dilute aqueous sugar solution, such for example, as sweet water, is supplied through a line 52. The contents of the tank 51 is heated by a steam coil I-53 immersed therein to a temperature of about 170 to 180 degrees F., and a motor driven mixer 54 may be provided for thoroughly mixing the contents of the tank 51 to maintain it in a fluid state. When the impure sugar solution is molasses it may have a Brix value of about 80 and if the amount of sweet water from the line 52 is insufiicient to reduce this value to about 60, additional water should be added. The effluent from the tank 51 is pumped by a pump 55 through a line 56 to a plurality of columns 57 and 58 which are substantially lilled with a granular activated bauxite having a mesh size of about 12 by 20. In addition to removing monovalent ions from the sugar solution, the bauxite bed also functions as a mechanical lilter to remove entrained solids from the solution as it passes therethrough.

The columns -57 and 58 are alternately used so that the etliuent from the tank 51 Hows through one of the columns while the bauxite from the other column is being renewed. Suitable valving, not shown, is used for this purpose. The etlluent from one of the other columns 57 and 58 passes out of the top of that column into a line 59 which feeds into a column 60 containing a bed of ion exclusion resin of either the cation or anion type as is used in the column 21 in the embodiment of FIG. 1 described hereinabove. The column 6l) is operated in the same manner as is column 21 to provide a plurality of fractions beginning with an eiiiuent which is substantially free of sugar and containing a high concentration of the impurities from the initial sugar solution, a second fraction containing some sugar but also including a high concentration of impurities, a third fraction which is a substantially pure sugar solution having a concentration of about 40 degrees Brix and finally a fourth fraction which is a pure but an extremely dilute aqueous sugar solution having a Brix value less than 40.

The third fraction, namely, the purified concentrated sugar solution is fed from the column 60 through a line 62 to a second mixing tank 63 wherein powdered activated carbon is added thereto to inhibit the growth of thermotiles and to improve the color of the sugar solution. A motor operated mixer or agitator 64 is disposed in the tank 63 to thoroughly mix the carbon particles with the sugar solution.

The eflluent from the tank 63 is pumped by a pump 6-5 through a line 66 to a iilter 67 wherein the carbon particles are removed by the deposition thereof on a filter cake on the filter elements of the ilter. The filter 67 may be of any suitable type for removing the line carbon particles from the sugar solution. For example, it may be a pressure type leaf or tube filter. The eliiuent from the filter 67 is fed through a line 68 to an evaporator 69 wherein water is evaporated from the solution to increase As the bauxite in the columns 57 and x58 becomes spent, it must be replaced. In accordance with the present invention fresh bauxite is periodically added in small amounts to the tops of the columns 57 and 5-8 from a pair of pressurizable feed tanks 71a and 71b and an equal amount of spent bauxite is removed from the bottoms of the columns through a pair of lines 72 and 73 and fed to respective washing tanks 74 and 75. The spent bauxite in tanks 74 and 75 is washed by flowing water therethrough from a line 76 and the liquid efuent from these tanks is supplied to a retention tank 77 through a line 78.

The bauxite granules from the tanks 74 and 75 are fed through a line 79 connected to both tanks to a pair of hoppers 80 and 81 and from these hoppers to a conveyor belt 82 driven by a motor 83 which drops the semi-dry bauxite into a kiln 84. The hoppers 80 and 81 are alternately fed by the tanks 74 and 75 and in turn alternately feed the conveyor belt to provide an additional retention time during which more liquid may low olf to the tank 77. yIn the kiln 84, the bauxite is heated to a temperature of about 600 degrees F. to burn oft the impurities carried on the surface of the bauxite granules and in the pores thereof. The thus purified bauxite from the kiln 84 is fed to a hopper 85 from which it is pumped by a pump 86 through a line 87 to a pair of hoppers 90 and 91 mounted above the feed tanks 71a and 71b and respectively connected thereto by means of lines 92 and 93.

As indicated hereinbefore, the columns 57 and 58 are alternately connected between lines 56 and 59. When the column 57 is connected between the lines 56 and 59 it is sealed oli from the line 72 and the feed tank while at the same time the column 58 is sealed off from the lines 56 and 59. During this period of time the feed tank is connected to the hopper 91 and fresh bauxite falls by gravity therein. Thereafter, and very brieiiy, as, for example, twenty to thirty seconds, the feed tank 71b is pressurized by a gas and connections bet-Ween the column 58 and the tank 71b and the line 73 are opened whereby a small pulse of fresh bauxite enters the top of the column 58 and an equal amount of spent carbon leaves the bottom. The column 58 thus remains lled with bauxite at all times. Similarly, while the column 58 is on line, i.e., connected between the lines 56 and 59, the bauxite in the column 57 is renewed. It will be apparent that since small amounts of bauxite are added to the top of the column to replace an equal amount of bamiite removed from the bottom of the column, the sugar solution passing up through the columns 57 and 58 lirst passes the most used bauxite and as it travels up through the bauxite bed it encounters fresher and fresher bauxite. During the time that the columns 57 and 58 are being respectively pulsed,

` the other column is on line so that the flow of effluent the Brix value of the sugar solution to about 60 to 70,

through the line 59 may be continuous if desired. It will be apparent, however, that only one column, 57 or 58 can be used if desired. During the time that tiow from the ion exclusion column 60 is interrupted, the flow through the filter 67 may also be interrupted to remove the lter cake from the filter elements.

If only a single ion exclusion tank 60 is employed, it will be apparent to those skilled in the art that the flow through the line 59 is not continuous. However, if a continuous flow is desired, two ion exclusion resin tanks can be provided and alternately connected between the line 59 and the line 62. In such a case, when one of the ion exclusion columns 60 is connected to the line 59, it will be disconnected from the line 62. At that same time the other column is connected to the line 62 and disconnected from line 59.

While the present invention has been described in connection with particular embodiments thereof, it will 'be understood that many changes and modilications of this invention may be made by those skilled in the art without departing from the true spirit and the scope thereof. Accordingly, the appended claims are intended to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed is:

1. A method of purifying an impure sugar solution such as:

molasses containing monovalent and multivalent cations, comprising the steps of: heating the impure sugar solution to about 170 F. to

contacting the heated impure sugar solution with bauxite to remove the monovalent ions therefrom,

passing the treated solution into a body of ion exchange resin particles capable of retaining in the pores of the resin particles a major portion of the sugar molecules while excluding a major portion of other solutes in said sugar solution, thereafter contacting said resin particles with water to wash out said sugar molecules and separating the effluent into a plurality of fractions wherein the solids in one of said fractions are primarily sugar,

mixing activated carbon particles with said one of said fractions,

removing said carbon particles from said one of said fractions, and then evaporating said one of said fractions to provide a purified sugar solution having a Brix value in the range of about 60 to 70.

2. A method according to claim 1 comprising the additional step of:

collecting from the effluent another fraction wherein the solids are primarily sugar and having a Brix value less than about 26, and

adding said another fraction to said sugar solution to be treated.

3. A method according to claim 1 in which said bauxite after being used to treat said sugar solution is oven heated to burn ofic the adsorbed solids and then reused to treat said sugar solution.

4. A method according to claim 1 in which:

said sugar solution is treated with bauxite by mixing particulate bauxite with said sugar solution, and comprising the additional step of filtering said particulate bauxite from said sugar solution before passing said solution into said body of ion exchange resin.

S. A method according to claim 1 wherein said sugar solution is treated with bauxite by:

providing a bed of granular bauxite, and

passing said sugar solution through said bed,

whereby said bed of bauxite lters entrained solids from said sugar solution prior to the passage thereof into said body of ion exchange resin particles.

6. A method according to claim 1 wherein said sugar solution is molasses having a Brix value of about 80, and comprising the additional step of:

adding an aqueous solution to said molasses to reduce the Brix value to about 60 before passing said solution into said body of ion exchange resin.

7. A method according to claim 6 wherein said ion eX- change resin is a strongly acid cation exchange resin com- 6 prising a sulphonated styrene-divinylbenzene polymer, said resin being a cross-linkage of divinylbenzene in the hydrogen form.

8. A lmethod according to claim 1 comprising the additional step of treating said one of said fractions with bauxite prior to said evaporating step.

9. A method according to claim -8 wherein the step of treating said one of Vsaid fractions comprises the steps of:

mixing particulate bauxite with said one of said fractions and then filtering the resulting mixture to remove the bauxite therefrom.

10. A method according to claim 9 comprising the additional step of reusing the bauxite filtered out of the sugar solution in said -treating of the impure sugar solution with bauxite.

11. Apparatus for purifying molasses, comprising:

a first mixing tank for receiving said molasses and an aqueous solution,

heating means in said tank,

a receptacle containing an ion exclusion resin,

a pump and conduits connected between said tank and said receptacle for pumping liquid from said tank through said receptacle,

a column of bauxite connected between said first mixing tank and said receptacle containing an ion exchange resin,

a second mixing tank,

a conduit connected between said receptacle and said second mixing tank for carrying a purified sugar effluent from said receptacle to said second mixing tank,

an evaporator, and

a filter connected between said second mixing tank and said evaporator for removing entrained solids from the efiiuent from said mixing tank before said efliuent is fed to said evaporator.

12. Apparatus according to claim 11 comprising:

filter means connected between said first mixing tank and said recep-tacle containing an ion exclusion resin for removing entrained solids from the effluent from said first mixing tank before passage thereof into said receptacle.

References Cited UNITED STATES PATENTS 2,868,677 l/l959 Kopke 127-46 B 2,937,959 5/1960 Roents 127-9 X 3,563,799 2/1971 Zievers 127-46 A 3,098,045 7/1963 Allegrini 252-455 R FOREIGN PATENTS 560,795 4/1957 Italy.

MORRIS O. WOLK, Primary Examiner S. MARANTZ, Assistant Examiner U.S. Cl. X.R. 127*46 B 

